Removing 27 dams opens up 600km of river for endangered migratory fish in Finland

Posted on 19 May 2020

WWF Finland has been removing dams and other barriers from rivers for more than three years now, together with a variety of partners - successfully opening 600 kilometres to migratory fish. And more removals are on the cards.

Dammed rivers and streams are the main reason why migratory fish in Finland are endangered - because hydropower dams and other barriers, such as incorrectly installed culverts and old mills, can prevent them from accessing breeding grounds, disrupting their natural life cycle.

“We started off with removing and replacing culverts in smaller creeks, before moving on to removing or bypassing the dams belonging to old mills and obsolete small hydropower stations. Now we have already contracts in place also to remove several hydropower dams in larger rivers,” explained Dr. Sampsa Vilhunen, head of marine and freshwater programmes at WWF-Finland.

So far over 600kms have been opened up according to calculations based on the Finnish Environment Institute's spatial data sets and the VESTY-database, which contains Finland's most comprehensive information on obstacles in its water bodies. The result is not the full total since the calculations do not include the smallest streams, which are excellent places for migratory fish to spawn and grow, so the total amount of re-opened habitat is actually considerably higher.

“We’re really happy with what we’ve accomplished, but this is just the beginning. There are tens of thousands of obstacles in Finland's rivers and streams, behind which tens of thousands of kilometres of potential fish habitats remain. So our work continues and luckily we are not the only ones now working on the subject," said Elina Erkkilä, WWF's leading freshwater expert.

The single largest reopening was achieved in 2019 when 126 kilometres was freed after WWF and the Centre for Economic Development, Transport and the Environment for South-East Finland built a bypass strip imitating a natural stream past the last dam that blocked the migration of fish on the Vaalimaanjoki River.

More than 100 kilometres of river water were also released to fish in Siuntio's Kirkkojoki River when WWF and the Uusimaa ELY Center built two nature-based bypasses around the old Munks dams. The fish routes were significant for two reasons: the original stock that lived in isolation above the dams now benefits from new genetic material, while endangered sea trout can now breed on the Lempansån rapids.

However, the number of kilometres does not always tell how significant the removal of obstacles has been.

“In some of the sites, the area opened is short, but the fish have been granted access to a natural habitat or a newly restored habitat, which is a real gem for reproduction. In addition, removing a dam is not only allowing fish migration, but typically brings back the rapids where the dam stood. Natural rapids are scarce as so many have been lost, which has had negative effects on freshwater biodiversity in general,” added Erkkilä.

According to Erkkilä, the demolition of dams is a unique way of fighting the decline in biodiversity. It is an action that is singular in nature, has predictable positive effects on biodiversity - that are also immediate and permanent.

“We’ve seen with our own eyes how the trout have returned to the opened area, even while the restoration works are still ongoing. We have also learned that with the removal of the last barrier, the official ecological classification of the water body has become excellent.”

WWF always removes barriers in cooperation with other actors. Indeed, local land and water owners, the Centres for Economic Development, Transport and the Environment, municipalities, cities, counties and other actors have all played a significant role in breaking down barriers and rehabilitating habitats.

Work is being done via various projects, funded either by the European Maritime and Fisheries Fund, the retailer K-Group’s ‘Mating belongs To All’ collaboration, or the ‘Freshabit’ EU LIFE IP. In addition, the support of the Lassi Leppinen Foundation has been a crucial enabler of the work. Not forgetting the large number of private citizens who support this part of WWF Finland’s work.

The next field season for removal of obstacles and the restoration of running waters will start in May when WWF, Metsä Board and the Pohjois-Savo ELY Center start the opening of two dams in Mämmenkoski rapids in Äänekoski. In addition, spawning pits and habitats for juvenile brown trout will be restored. The fieldwork, which will last for more than a month, will be carried out together with Mämmi's fishery.

“Opening dams and rehabilitating living and breeding habitats in Mämmenkoski will enable trout to migrate freely, and for natural fry production to come back to the rapids. It’s great that the connection is opening, as it has been planned for several years," said Manu Vihtonen, WWF's freshwater expert.

For the coming years, the WWF has already mapped fifty more dam sites where they want to work, which, if opened to fish, would free up hundreds - potentially thousands - more kilometers of free-range areas.

Restoration of free flowing waters also continues, as removing obstacles alone is not always enough to save migratory fish. Creating or restoring breeding and juvenile areas and improving the water quality in aquatic ecosystems may be needed to enable fish to reproduce successfully.

“The work is long-term and not everything is taken care of in one field season. We have only one goal: the work has to continue until there are no more useless dams in our waterways," said Erkkilä.